In wireless communications, uplink power deficits are a significant problem for emerging cellular data services. This problem arises from the following combination of cellular operators' targets: higher radio frequencies (than those of the voice service); higher bit rates; deep indoor penetration; and co-location with the existing voice-BS infrastructure.
Multi-tone modulation (OFDM) is attractive, as it is immune to channel dispersion and spectrally efficient; but the power deficit is especially hard with OFDM. The reason is the poor Peak-to-Average Power Ratio (PAPR) (the signal amplitude is Rayleigh-distributed, even in the case of QPSK-modulated tones). In the last case, PA back-off is limited by out-of-band emission; to meet regulatory spectral mask, it must be ˜10 dB.
Thus, a strong need exists for improvements in wireless communication systems, methods and apparatus.
It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or analogous elements.